Lot of good info here. The engine is completely apart, the crank has been polished, it has .030 on the block and .030 domed pistons (previous rebuild, I did not know it had been rebuilt or i would have just run it) I want to build it to last and have a bit of spunk. I am trying to go on the advice of the machine shop that the 10.5:1 will be problematic. I am trying to get a good rebuild for this commando 273.